The present invention relates to a method of tracing and recording image lines, which traces the contour of images recorded in a photo film or the line patterns of a line drawing, and records the image contour or the line patterns. The invention particularly relates to a method of producing a cut-out mask. Further, the invention relates to an apparatus for tracing and recording image lines.
In the printing of catalogues, photographs of goods in which a background is included must be masked to eliminate the background, so that only the picture of the goods to be illustrated is represented in a catalogue. A cut-out mask used for such printing is obtained through the following process. First a mask film is produced which has a transparent section exactly corresponding to the external outline of the goods and an opaque section exactly corresponding to the background of the goods. Then the mask is placed over the original film so that the external outline of the goods in the original film is exactly consistent with that of the mask film. The picture of the goods is then reproduced without the background. Also, such a cut-out mask is used to substitute another background in place of the eliminated background or to produce a negative image from a positive image. In these cases the relation between the transparent and opaque section is reversed.
The preparation of such a cut-out mask has conventionally been done by hand. That is, the cut-out mask has been obtained through the following process. First the contour of the image to be cut out is drawn on a transparent sheet in the same manner as a tracing. The area inside or outside the contour is then coated with opaque ink. Such operations require a skillful and proficient operator, and moreover much time is required. For these reasons masking of photographs has presented a serious problem in photoprocessing operations.
The Japanese laid open Specification No. 47-17501 discloses a method of producing a cut-out mask. According to that laid open specification the background of a required image is given a specific color for color photography. Then only the specific color of the background is taken out or eliminated with a processing color-scanner when the color image is duplicated. That method requires so much attention to the photography that it has not been widely adopted.
Another Japanese laid open Specification No. 55-57846 (Japanese Application No. 53-131195) discloses a method of producing a cut-out mask which attempts to solve the above disadvantages. According to that specification detector elements such as photo-electric convertors are used to combine automatic traces of the detector elements with a manual trace drawing. A detector is divided into eight elements 1-8, as shown in FIG. 1 which is a plan view of a prior photoelectric element. However, that method has the disadvantages that, when the photo film including an original image has fold lines extending across the outline of the goods to be cut out, the detector elements trace the fold lines, diverging from the contour to be traced, and, when the original image has any border lines of different thickness which may easily be mistaken for the contour lines within the image area to be cut out, the detector elements trace the border lines in error. Accordingly, the detector is arranged so that the required image contour is traced and recorded automatically in a straight or gradual curve portion, based upon signals from the detector elements, and when the contour of the required image has fold lines or border lines, the automatic trace produced by the detector elements is stopped and the contour is traced by hand at these portions.
The prior arts as mentioned above, however, cannot thoroughly solve the conventional disadvantages.